How to mux a timed audio to another video

[infected]

I have 2 source videos which i have to merge

Source 1 - good video/bad audio in .mkv format ..... i want to use video stream of this source [h265]
Source 2 - bad video/good audio in .mkv format ..... i want to use audio of this source

now when i mux the 2 source in mkvmerge then the audio is 5 min. less in length so to varify i have demuxed the source 2 and found that the audio was timed in source 2 to get the synced result

Now my question is

Q1. how do i mux video of source 1 with timed audio of source 2
Q2. is there any software to check the exact split timing [millisecond] of the source 2 audio

this aint repost

[sneaker_ger]

If the audio tracks are synced to different videos (like one to 23.976 fps and the other to 25 fps) you have to either convert the audio (with e.g. eac3to) or change the fps of the video track in mkvmerge when muxing. You can see the delay with MediaInfo or extract the timecodes with mkvextract (first timecode = delay).